Packing boxes are often used to pack food, cosmetic, stationery and decoration. When a packing box is made, the packing box has a fixed volume. The packing box will occupy the same space whether the packing box receives goods or not. Therefore, the conventional packing box needs large space to store and transport, which increases cost of storage and transportation.
To solve the above mentioned problems of packing boxes, a foldable packing box has been provided. The conventional foldable packing box includes a plurality of foldable connecting boards. During transportation, the connecting boards are folded to locate at a same plane for saving space, so as to reduce transportation cost. The conventional foldable packing box is usually made of a comparatively thin single layer paper board through cutting a whole piece of paper board and then forming folding lines according to the shape of the box. However, this kind of foldable packing box made of a comparative thin single layer paper board is not fit to receive comparatively heavy goods. So, it is necessary to design a kind of foldable packing box made of a comparative thick paper board.
Furthermore, a conventional non-foldable packing box, such as a top and bottom type of packing box which has outer and inner boxes engaged with each other, can provide high weight capacity and aesthetic sensibility with comparatively low cost. A thick core board which is a conventional composite paper board having comparatively low price and high weight capacity is used to form a blank box with the fixed shape of packing box. Then, an inner layer paper and an outer layer paper are separately pasted to the inner surface and outer surface of the blank box. The edge of the outer layer paper is also pasted to the edge of the inner surface. The inner layer paper is pasted to the inner surface, and covers the edge of the outer layer paper to increase aesthetic sensibility of the packing box. However, since the core board is pasted after it is formed with the fixed shape, the pasting process needs complicated manual positioning, which results in low production efficiency and high product cost. Particularly, when the packing box has curve side edges, the operation of pasting is hard to implement.